nixos/modules: Remove all usages of types.string

And replace them with a more appropriate type

Also fix up some minor module problems along the way

nixos/modules/services/networking/hostapd.nix

@@ -81,7 +81,7 @@ in
       driver = mkOption {
         default = "nl80211";
         example = "hostapd";
-        type = types.string;
+        type = types.str;
         description = ''
           Which driver <command>hostapd</command> will use.
           Most applications will probably use the default.
@@ -91,7 +91,7 @@ in
       ssid = mkOption {
         default = "nixos";
         example = "mySpecialSSID";
-        type = types.string;
+        type = types.str;
         description = "SSID to be used in IEEE 802.11 management frames.";
       };
 
@@ -119,7 +119,7 @@ in
       group = mkOption {
         default = "wheel";
         example = "network";
-        type = types.string;
+        type = types.str;
         description = ''
           Members of this group can control <command>hostapd</command>.
         '';
@@ -135,7 +135,7 @@ in
       wpaPassphrase = mkOption {
         default = "my_sekret";
         example = "any_64_char_string";
-        type = types.string;
+        type = types.str;
         description = ''
           WPA-PSK (pre-shared-key) passphrase. Clients will need this
           passphrase to associate with this access point.